Etching machine



Dec. 2, 1930. R. R. ROBERTSON ETCHING MACHINE Filed Oct'. 8, 1929 3 Sheets-Sheet l Dec. 2, 1930. R, R, ROBERTSN 1,783,390

ETCHING MACHINE Filed oct. s, 1929 5 sheets-sheet 2 P v i 3G 3 Dec. 2, 1930. lR. R. ROBERTSON 1,783,390

ETCHING MACHINE Filed Oct. 8, 1929 3 Sheets-Sheet 5 C D D Patented Dec. 2, 1930 EOBEET E. ROBERTSON, E EvANsToN, ILLINOIS ETCHING MACHINE Application filed October, 8, 1929. Serial No. 398,117.

This invention relates to a means through which the surface of a printing plate required to be etched, in the course of its production, is subjected to the reagent employed for etching it; and has for its object to provide a means whereby the surface to be etched can be subjected with greater uniformity and with greater certainty with respect to the duration of the treatment than `with apparatus as heretofore constructed.

Accordingly, the invention proceeds upon the principle of mounting the metal to be etched for movement across an exposure opening Where it will encounter the reagent; the

exposure opening being of less area than the entire surface to be treated, so that the surface is treated progressively and the severity of the treatment being regulated by the rapidity of motion of the surface'past the 2o exposure opening the number of times the surface is made to traverse the exposure opening, the volume of reagent delivered tothe surface per unit of time of'travel, or some or all of thesevfac-tors together; an important ,25 feature of the invention residing in the circumstance that 'whatever the condition encountered by the surface at the exposure opening and whether the entire area of the exposure opening be subjected tov identical supply of the reagent, all portions of the surface to be etched will be made to traverse, alike, one dimension of the exposure opening and therefore receive identical treat-ment,

Y particularly if the manner and volume of delivery of the reagent be uniform throughout that dimension of the exposure opening which is perpendicular to the direction of travel of the surface. Y

The preferred embodiment of the invention includes as a means for bringing the reagent to the surface that is to be etched, a rotary dasher dipping into a bath of the reagent and throwing it by centrifugal force against the surface, and contemplates also the use of means for evacuating gases from withinthe vat to avoid contaminating the Working atmosphere around the machine, and also with the eifect of maintaining the required supply of free oxygen in the presence of the etching operation; and the Ventilating apparatus employed to this end is such that flow of air through the exposure opening and past the surface that is being treated will be inward rather than outward. But it is to be understood that the invention in its broadest aspect is not limited to any particular means for bringing the reagent to thesurface that is to be etched, or the use of Ventilating means.

In the accompanying drawings, in which the preferred embodiment of the invention is shown by way of illustration- Figure l is a vertical section of an etching p machine, the plane of section being indicated approximately by the line la-1m of Figures 2 and 3. Y

Figure 2 is a sectionon the line Qm-Qm of Figures l and 3; and

Figure 3 is a top plan view of the machine with the ventilator stack in section.

l represents a vat which is preferably constructed of vitreous material or earthenware, Y inform suitable to contain al relatively shallow bath A of etching reagent. Vat l is constructed with an exposure opening 2 conveniently defined by supporting removable plates 2a, 2b upon the ledge la around the perimeter of the upper open end of the vat. The invention contemplates having the surface that is to be etched travel in a manner to bring all parts of such surface successively but uniformly into the range of the reagent which is i delivered at said opening.

I As a preferred means for mounting ai plate, for instance, a printing plate B, in position to' traverse'thel exposure opening 2, I employ a rotary cylinder 3 mounted upon a shaft 4: and receiving motion through some suitable means, such, for instance, as al pulley 5 receiving a belt 6 that also passes around a. pulley 7 mounted on shaft 8 that is driven by electric motor 9`. Plate B may be replaceably mounted upon cylinder 3 through suitable anchoring means, such, for instance, as screws 3a gripping one margin of the plate and a cleat 8b that is attached to the cylinder through means of screws 3c, and securing the opposite margin of sai/d plate B through means Vof screws 3d coniningit to the cleat 3e which is secured to the' cylinder 8, with adjustment in the direction to place the plate B under tension, by means of anchoring hooks 3f and thr xa ded sleeves 3g. As suggested in Figure 2, cylinder 3 will be provided with appropriately arranged holes 3h adapting it to receive bolts, such as shown' at 23o, and hooks 3f at positions appropriate to the length ot the plate 'hat is to be treated.

In creer to cast or project etching reagent A against the surface et a plat` traversing the exposure opening 2, I prefer to employ a r tary dasher 1() conveniently mounted ou the shaft S so that it is rotated by the driving motor l), and this dasher is caused to dip into the bath il.. suticiently to pick up and discharge the reagent by centrifugal 'force upwardly through the exposure opening where it will iinpinge against the surface et the plate Il as the latter traverses said opening. lf`rei`erably, the exposure opening 2 is vertically above the dasher lO, for the reason that the discharge from the dasher 'that reaches the surface ot the plate in this relative position is in much better condition, consistent with the needed volume of the reagent, than if the exposure opening were located at any other point in the sector oi" travel of the dasher.

In order to ventilate the interior of the vat 1, tan 11 has its eye 11a in con'nnunication through suction pipe 11b with the interior of the "at, the tangential discharge port 11o of the fan being equipped with a staclr 12 through which the fan can deliver to a point in the outer atmosphere that will be unobjectionable. Suction pipe 11b communifates with the vat 1 through a port 13` which is preferably located at the middle upper pointA in one side of the vat 1, and in order to properly aerate the interior of the vat, the latter is provided. with an air supply flue 14 at the opposite side of the vat and preferably having a horizontal dimension approximately equal to that of said side, and having its inner defining wall 14al extending` downwardly within the vat so as to locate tue delivery end 1lb of said flue well down within the vat to avoid .interference between the incoming air and the spray of reagent, besides more thoroughly aerating the interior ot the vat. lVhile the sectional area of the flue 111 will be sufficient to supply approximately all of the air evacuated by the fan l1. some air will flow inwardly through the exposure opening 2 so as to displace inwardly tumes arising 'from the operation and maintain supply ot free oxygen that may be needed at the surface where etching is taking place. Fan 11 may be conveniently driven by connecting its pulley 11d through belt 15 with pulley 16 on the shaft 8.

17 represents trapping recesses in the walls of the iat 1 surrounding the shaft 8 and preventing escape of the reagent through the openings made to receive said shatt; said trapping recesses being constructed to drain bacli into the Vat; and the openings on the inner and outer sides of said recesses being guarded by centrifugal disks 18 and 19 which throw oft any liquid precipitating upon and tending to move outward along the shaft.

In the operation of the device, the rotation ot the cylindrical plate carrier 3 and that of the spray dasher 10 are definitely related by proper selection of dimensions of driving connections. As will best be seen from Figure 2, the dasher approximates the dimein sion of the exposure opening 2 in a direction transverse to the travel ot the carrier, with the result that it develops a characteristic and substantially uniform discharge of reagent in any given line parallel with the dasher; and as all parts off the surface to be etched cross said line, or, indeed, all ot' all lines running in that direction, all parts of the surface receive like treatment. The depth et etching can readily be controlled by the number ol times the plate is caused to traverse the exposure opening; that is, in the particular form illustrated, the number et times the rotary carriage is caused to revolve.

I claim:

1. In apparatus of substantially the character described, means defining an exposure opening, means for delivering a iiuid at said opening, and a plate carriage mounted for movement and adapted to present portions ot a. plate successively to said exposure opening.

2. In apparatus of the character described, means defining an exposure opening, means for delivering a fluid at said exposure opening, and a carriage adapted to receive and hold a plate and movable in a manner to cause the plate to traverse the exposure opening with a continued unitorm movement.

3. In apparatus of the character described, means for delivering a fluid over a predetermined area, and a carriage adapted to receive and hold a plate; said carriage having a movement which causes the surface ot the plate mounted thereon to traverse said arca of delivery.

4l. In apparatus of the character described. a rotary plate carrier adapted to receive and hold a plate, and means delivering a fluid over an area corresponding to ay portion of the surface ot said carrier; said carrier having means tor moving it to cause successive portions of the area of the plate mounted upon it to traverse said area.

5. In apparatus of the character described, a vat having an exposure opening, means within said vat for delivering fluid contained by the vat at said exposure opening, and a rotary carriage adapted to receive and hold a. plate and by its rotation present successive areas of said plate at said exposure openinc.

6. In apparatus of the character described, a vat, a rotary spray dasher in said vat, and means for mount-ing a plate and causing its surface to progressively intersect a Zone of delivery from said dasher.

7 In apparatus for etching plates, a rotary carriage, a cleat mounted on said carriage and adapted to receive one margin of a plate to be etched, and an adjustable anchoring means on said carriage adapted to receive the opposite margin of such plate; said anchoring means comprising a movable cleat, a hook adapted to engage said carriage, and means for adjusting the hook relatively to said movable cleat.

8. In apparatus of the character described, a vat having an exposure opening, a carriage adapted to mount a plate and cause said plate to traverse the area of said exposure opening, and means for drawing air from the interior of said vat.

9. In apparatus of the character described, a vat having fluid delivery means, an exposure opening at Which fluid is delivered, a movable carriage adapted to mount a plate and cause it to traverse 'said opening, means for withdrawing air from the interior of said vat, and means for admitting replacement air constructed to release infiovving air at a point remote from said exposure opening.

l0. In apparatus of the character described, a vat constructed With an exposure opening in the upper portion thereof, means Within the vat for delivering fluid at said opening, a movable carriage adapted to mount a plate and cause the .surface of the plate to traverse said exposure opening, means for exhausting air from Within the vat, and an intake flue leading downward along one Wall of said vat and releasing replacement air at a level belovv the exposure opening.

Signed at Chicago, Illinois, this 4th day of October, 1929.

ROBERT R. ROBERTSON. 

